In recent years, ingots (referred to also as strands) of steels or various kinds of alloys or the like are mass-produced generally by using a so-called “continuous casting method” which includes the steps of continuously injecting the molten metal in a melting state into a water-cooled mold and gradually drawing out solidified ingots from the mold.
In order to obtain high-quality ingots with less non-metallic inclusions and less component segregation by the above-described continuous slab casing, it is important to stir the molten metal in the middle of the solidification process as required. Also, the molten metal stirring in case of the slab that is larger in a cross-sectional area and moreover larger in length-to-width ratio of the cross-sectional shape (e.g., the ratio of the length of the longer side wall to the length of the shorter side wall being 5 or more) would be highly liable to such problem as occurrence of center segregation, center cross-sectional cracks as well as degradation of machinability, unlike the case of strands that are small in cross-sectional area and moreover nearly square in cross-sectional shape such as blooms or billets, for this reason there has been a need for stirring the molten metal as required.
Recently, as the life-span of submerged nozzles or the like becomes longer, the service life of the submerged nozzles or the like becomes durable to the casting with a plurality of ladles, which makes it possible to continuously cast the different kinds of steels and the strands of the cooling molds in different widths.
Various kinds of structures for stirring the molten metal as required have been proposed for a long time, but there is still no countermeasure enough to deal with the casting when the width or the thickness of the mold are changed.
The applicant of the present invention discloses the continuous slab casting apparatus, in Japanese Patent No. 5,742,992, wherein a rotational mechanism rotates a platform (hereinafter called a base) having a connecting mechanism (hereinafter called a nozzle exchanging-holding mechanism) connecting the submerged nozzle to a slide nozzle mechanism, together with the submerged nozzle, by a specific angle. According to such configuration, as well as the rotational flow can be obtained by keeping a discharge direction of the molten metal discharged from a discharge hole on a lower end of the submerged nozzle toward an objective direction of a longer side direction, it is possible to keep the rotational angle corresponding to the length and the thickness of the longer side.
FIG. 1 is a front view of the continuous slab casting apparatus disclosed in Japanese Patent No. 5,742,992, and FIG. 2 is a plan view (bottom view) of the apparatus looked up from a bottom. The conventional continuous slab casting apparatus is provided with a slide valve mechanism to adjust the flow quantity of the molten metal flowing into the mold, and the nozzle exchanging-holding mechanism to hold the submerged nozzle guiding the molten metal from the slid valve mechanism to the mold on a lower side of the slide valve mechanism and also to exchange an after-use submerged nozzle with an unused submerged nozzle. The continuous slab casting apparatus disclosed in Japanese Patent No. 5,742,992 is also provided with those mechanisms, and further provided with a nozzle rotational mechanism as described herein after.
The slide valve mechanism is placed between a housing 5 and a seal case 9 on a lower surface of a tundish 1, and its configuration is well-known, so undermentioned description refers only to necessary parts to the present invention. A slide plate 3b is placed between an upper plate 3a and a lower plate 3c, and slides by a hydraulic cylinder 7 for sliding, whereby the size of a molten steel hole made on each plate can be changed. Accordingly, it is possible to adjust the flow rate of the molten metal supplied from the tundish 1 through an upper nozzle 2, and supply the molten metal to a submerged nozzle 6 through a lower nozzle 4.
The lower nozzle 4 is placed at a position corresponding to the molten steel hole on the lower plate 3c of the seal case 9, and functions as a role of connecting the slide valve mechanism to the submerged nozzle 6.
The nozzle exchanging-holding mechanism is incorporated to the base 11 placed on a lower side of the seal case 9.
The base 11 is integrally formed by connecting two pieces 11a and 11b with a connecting bar 11c, wherein the pieces 11a and 11b are arranged on both directions (hereinafter referred to right and left directions, or right and left) perpendicular to a moving direction of the submerged nozzle 6 (hereinafter referred to a nozzle moving direction: an arrow direction of FIG. 2) at the exchange of submerged-nozzle. At a center of the right and left pieces 11a and 11b, a space (hereinafter referred to a moving-connecting space D) is arranged so as to move the submerged nozzle at the exchange of the submerged-nozzle and to be connected to the lower nozzle 4 at fixing (operating) the submerged nozzle 6. A right-and-left width of the moving-connecting space D is corresponding to a right-and-left width of a flange 15 on an upper end of the submerged nozzle 6, and a slide guide 14 is disposed on an inside of the moving-connecting space D along the nozzle moving direction. The flange 15 on the upper end of the submerged nozzle 6 is pressed against the lower surface of the lower nozzle 4 and held thereon, according to the undermentioned configuration.
On the both right and left sides of the moving-connecting space D under the lower surfaces of the right and left pieces 11a and 11b of the base 11, plural clampers 13 are supported by clamper pins along the nozzle moving direction, so as to position the tips of the clampers on the lower surface of the flange 15 of the submerged nozzle 6. Coil springs 12 attached on the base 11 are arranged on ends of the clampers 13, and the tips of the clamper 13 are biased upward. Accordingly, the lower side of the flange of the submerged nozzle 6 is biased upward at the tips of the clampers 13, and the upper end surface of the submerged nozzle 6 is tightly attached to the lower surface of the lower nozzle 4.
Furthermore, the continuous slab casting apparatus is configured so as to exchange an after-use submerged nozzle 6e with an unused submerged nozzle 6n by means of the nozzle exchanging-holding mechanism.
The nozzle exchanging-holding mechanism is configured so that the unused submerged nozzle 6n inserted from a guide rail 16 on an upstream side of the nozzle moving direction moves to a downstream side of the nozzle moving direction, and pushes out the after-use submerged nozzle 6e to the guide rail 16 on the downstream side. At this time, the connecting bar 11c of the base 11 is configured so as not to interfere with the moving of the submerged nozzle 6, as shown in FIG. 1.
In the conventional continuous slab casting apparatus, the base 11 is configured to be fixed on the seal case 9, but the apparatus disclosed in Japanese Patent No. 5,742,992 that the present invention presupposes is configured so as to allow the base 11 to rotate a specific angle by means of the rotation mechanism.
The base 11 is suspended from the seal case 9 by a support guide roller 22 and a support guide 21 so as to be rotatable around a center axis of the submerged nozzle 6, so that driving a driving device (hydraulic cylinder) 23 fixed on the seal case 9 under such condition can rotate the base 11 by a specific angle. Accordingly, the submerged nozzle 6 held by the nozzle exchanging-holding mechanism rotates, too, and the discharge direction of the molten metal from the discharge hole can be changed according to the conditions.